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Re: Mini-volcano



On 11/9/01 11:47 AM, E.L. Jossem wrote:

IMPORTANT SAFETY NOTE: There is some controversy about the hazards of
this experiment. While it has been used for many years in education,
some chromium compounds have been found to be carcinogenic.

This isn't an experiment, it's a neat demo that someone saw once and said,
"Hey, that looks just like a volcano, cool!" Cool demos are always popular,
so it made its way into a lot of classrooms.

Is it really worth it to introduce toxic compounds into the classroom for
the sake of something that looks cool? Does this demo serve an educational
purpose? Yes, it mimics the growth of a volcano, but wouldn't actual video
footage of a real volcano be as (or more) instructive?

If you are looking for a good demonstration of a decomposition reaction,
there are safer alternatives (although perhaps not as spectacular). Heating
a hydrate to drive off the water (CuSO4.5H2O shows a nice colour change) and
then adding water back and feeling the heat released interests the students,
and it's one they can do themselves.

Sorry to be so negative, but over the past few years I have been
re-evaluating the demos I do, in the interest of good pedagogy. I would
still like to do lots of demos, but I want to do more where the student has
learned something in the class, sees the demo and thinks "aha!" (Or,
obviously, the reverse case where I do the demo and spark student interest
in learning more.)

Mike
--
Michael Porter
Colonel By Secondary School
Ottawa, Ontario, Canada